A Quick Guide to Field Sobriety Tests, PBTs, and Breathalyzers

With the exception of sobriety checkpoints, the police in Virginia must see something wrong before they can pull you over. If a police officer pulls a driver over for DUI without a legal justification, anything that officer discovers afterwards is inadmissible at the trial.

Even after the police have pulled a driver over, the police are limited as to what they can do. If the stop was for a moving violation, the police can only detain the driver long enough to run a background search and write a ticket unless they discover evidence of another crime.

If a police officer wants to do more than write a ticket, the officer needs evidence of intoxication to justify further actions. He must see erratic driving (for example, driving very slowly, straddling the line, hitting the curb, or driving in the wrong lane), or, after pulling over the driver, he must find other indicators such as glassy or blood shot eyes, slurred speech, the odor of an alcoholic beverage, an open container, or a lack of coordination.

When an officer sees any combination of these things, he may decide to ask you to step out of the car and take a field sobriety test (FST) or blow into a preliminary breath test (PBT). Both of these tests are voluntary.

Field Sobriety Test (FST)

FSTs are a series of exercises or tests used to determine sobriety. Most of the tests examine two things: 1) motor control and balance and 2) the ability to follow instruction. Many of these tests are difficult even for a sober person. You are not legally required to submit to FSTs.

In 1981 the National Highway Transportation Safety Administration (NHTSA) developed standardized field sobriety tests to be used by law enforcement nationwide.

The three official NHTSA tests include very specific versions of the one-leg-stand, the nine-step-walk-and-turn, and the Horizontal Gauze Nystagmus tests.  While the Standardized Field Sobriety tests (SFST) developed by NHTSA are rigorously followed in many states, Virginia has no particular standards for administering FSTs.

The FSTs used by the police in Virginia vary between regions, jurisdictions, and individual officers. Often, officers use variations of the same test that may or may not resemble the NHTSA tests.

Some of the typical tests in Virginia include:

•  The Nine Step Walk and Turn (walking heel-to-toe on a straight line, and then turning and walking back a specific number of steps)

•  The One Leg Stand (standing on one leg without moving your arms and legs)

•  Saying the alphabet, starting from a random letter and progressing forward or backward

•  Counting between two given numbers, either forward or backward

•  Touching your nose

•  Touching your thumb and fingers while counting.

•  The Rhomberg Balance test (also known as the internal clock test) (close eyes, tilt head back, and stand still for 30 seconds)

•  The Horizontal Gaze Nystagmus test (HGN) (following a pen or finger with just your eyes).

The Nine-Step-Walk-and-Turn

The “walk-and-turn” test has several variations in Virginia but usually involves an officer asking a driver to stand on a line (real or imaginary) with their right heel touching the toes of their left foot while keeping their arms at their side.

While holding this position, the driver is given instructions on how to perform the test. The driver then takes nine steps heel-to-toe along the line, turns 180 degrees by taking a series of small step, and walks nine steps back.

During the test, the officer looks for eight clues of intoxication.

1) Cannot maintain instructional position

2) Starts test too soon

3) Stops while walking

4) Not walking heel-to-toe

5) Steps off line

6) Use arms for balance

7) Loses balance on turn or turns incorrectly

8) Takes wrong number of steps

According to NHTSA, a driver must exhibit two of these eight clues in order to have “failed” the test. Virginia courts usually do not have a standardized definition of failure.

According to NHTSA, in order for this test to be accurate the ground where the test is performed must be dry, hard, level, nonslippery with sufficient room to maneuver. It cannot be too close to traffic either. If you had to take this test under any of those conditions, notify your attorney immediately.

This test’s accuracy is questionable if the driver is over 65 years old or has back, leg or inner ear problems (or any medical issues that affect balance or muscle control). This test should not be performed in heels that are more than two inches high or other footwear that makes it hard to balance (such as shape-ups, flip flops, or perhaps even barefoot.)

If there is anything that made your test extra difficult tell your attorney immediately.

The One Leg Stand

The one leg stand begins with the driver standing at attention while the officer provides instructions. The driver is asked to lift one leg six inches off the ground while keeping his knee strait, arms at his side, and eyes on his elevated foot. The driver then counts “one one-thousand, two one-thousand” etc. until told to stop (usually after 30 seconds).

While there are several variations of this test in Virginia, normally the officers are looking for four clues of intoxication.

1)  Sways while balancing

2)  Uses arms to balance

3)  Hops

4)  Puts foot down

NHTSA guidelines state that a person who exhibits two or more clues, fails the test. In Virginia, most judges use their own experience and discretion to determine what is a failure.

The one-leg stand should be performed on a dry, hard, level, and non-slippery surface. The driver should not be over 65 years old or more than 50 pounds overweight. He or she should not have back, knee, or inner ear problems, and should not be wearing more than two-inch heels.

Weather conditions, traffic, distractions from the officer, and countless other things can also invalidate the results of the one-leg stand test. Talk to your attorney about any conditions that made it hard for you to perform this test.

Horizontal Gauze Nystagmus (HGN)

There is one FST that does not have anything to do with coordination and little to do with instructions: the Horizontal Gaze Nystagmus (HGN) test. Nystagmus is an uncontrollable tremor of the eye. All people have some nystagmus but intoxication causes it to become more readily observable in most people.

The HGN test involves an officer holding a stimulus (a finger or a pen) in front of the driver’s face while watching the driver’s eyes.

Before the HGN test begins the officer looks for nystagmus while the eyes are resting. If the officer sees resting nystagmus the HGN test is void.

To begin the test, the officer has the driver hold their head still while following the stimulus with their eyes. The officer smoothly and slowly moves the pen or finger back and forth across the driver’s face and slightly above their eye line. First the officer looks to see whether the driver’s eyes smoothly track the stimulus, then the officer sees whether the driver’s eyes quiver while focusing on the extreme left and right, and finally the officer looks for nystagmus when the eyes focus on the stimulus at less than a 45 degree angle.

According to NHTSA, the HGN is failed if the officer observes nystagmus in both eyes under at least two of the three conditions (e.g. eyes do not track smoothly and nystagmus at the extreme left or right).

A driver may exhibit nystagmus for several reasons other than intoxication, including medical conditions and officer error.

If the officer holds the stimulus too high it can create nystagmus. If the officer moves the pen too quickly back and forth it can cause nystagmus. If the test is administered in a location where there are quickly moving objects within the driver’s field of view (e.g. cars on the freeway) it may cause nystagmus. If an officer performs the HGN test repeatedly or takes too much time performing the test, the driver’s eyes may become fatigued and exhibit nystagmus.

Because the correlation between intoxication and nystagmus is not something that the average person understands, some Virginia courts will not allow or give weight to HGN tests in a DUI trial. However, if you were given the HGN test make sure to talk to an attorney to determine whether the test was administered accurately and whether it may be used at trial.

Preliminary Breath Test (PBT)

There are two types of breathalyzers used in Virginia: 1) the preliminary breath tester (PBT) and 2) the evidential test device (ETD). The biggest difference between these machines is that the PBT is voluntary—you have the right to refuse blowing into a PBT! On the other hand, ETDs are usually mandatory if you have been arrested for DUI. You may be charged with refusal to submit to a breath test if you refuse to blow into an EDT!

A PBT is a handheld device that police officers use on the side of the road to determine a driver’s blood alcohol content (BAC). It is a small, portable machine with a plastic tube or mouthpiece that the driver blows into. A PBT can only be used to justify an arrest; it cannot be used as evidence in a trial. Submitting to a PBT test is completely voluntary.

An ETD is different from a PBT in several ways. For one, it is not portable. The machine is about the size of a large shoebox with a blow tube that sticks out from the side. For another, an ETD is usually attached to a printer and keyboard. All ETDs in Virginia are the same make and model (INTOX EC/IR II’s), and are kept at the police station rather than in police cruisers. Before blowing into an EDT in Virginia, a driver must be observed for 20 minutes. The driver must also be read a form letter stating that he must submit to the test, that he has the right to observe the results, and that he has the right to receive a copy of the printed results. The results of an EDT test can be used as evidence at trial.

Remember, the most important difference between PBT and ETD tests is that a driver suspected of DUI does not have to submit to a PBT test, whereas a driver arrested for DUI must submit to an ETD test or face the charge of “refusal to submit”.

PBTs are just machines, and, like all machines, they break. If a faulty PBT reading is used to arrest a driver, that arrest may be dismissed.

The PBT measures BAC with a fuel cell that mixes a sample of breath with a chemical called platinum phosphoric acid. The alcohol and chemical react to create an electrical charge. A voltammeter in the PBT measures how much electricity is created and calculates the driver’s BAC.

While PBTs are very convenient, they are less accurate than ETDs. Consequently, Virginia law states that the results of PBTs cannot be used against a driver in trial as proof of intoxication (Va. Code § 18.2-267(E)). Also, the law says that, unlike the ETDs found at the police station, drivers are not required to blow into PBTs. Any driver in Virginia who is accused of DUI may refuse to blow into a PBT, and his refusal cannot be used as evidence of guilt.

However, if the driver voluntarily submits to taking a PBT, the police can use the PBT results as evidence that the driver was justifiably arrested for DUI. Do not agree to blow into a PBT.

In order to use a PBT to justify an arrest, the police must do four things: 1) they must use an approved brand and model of PBT; 2) they must use and maintain the PBT according to the manufacturer’s instructions; 3) the PBT must be properly calibrated; and 4) the officer must inform the driver of his right to see the results of the PBT.

The law requires the PBT to be used according to the manufacturer’s instructions, but it is unfortunately quite common for the police to ignore or forget those instructions. For example, the Alco-sensor III must not be used if the machine’s temperature is below 59° F (15° C) or above 96° F (36° C). However, most officers keep their PBT in the trunk of their patrol car where the machine is either very cold or very hot.

Also, many PBTs are vulnerable to radio frequency interference (RFI) or radio signals from police officers’ communications devices. Radio signals that strike the extremely sensitive voltammeter can cause sporadic readings. If the digital read-out flickers or the screen blanks instead of providing a reading, then RFI may be influencing the PBT. If you see an officer using his radio near the PBT or having any of these problems, tell your attorney.

PBTs cannot distinguish between alcohol fumes found in the blood and those found in the mouth or stomach. The PBT will likely give an erroneously high reading if the driver burped, vomited, or drank alcohol within 20 minutes before the test.

Because PBTs ride around in the trunks of police cars all day, they need to be tested periodically and certified as accurate. There are guidelines for the regular calibration of PBTs and ETDs which a good attorney may use to get a PBT result excluded from evidence.

Evidential Testing Devices (ETD)

Drivers who are arrested for DUI in the Commonwealth of Virginia are brought to the police station to have their BAC tested with an Evidential Testing Device (ETD). All ETDs in the Commonwealth of Virginia are the same make and model: INTOX EC/IR II.

Before an ETD test, the driver must be observed for at least 20 minutes. If he burps, vomits, or places anything in his mouth during the 20 minutes, the driver’s mouth must be cleaned out and the police must then observe him for another 20 minutes.

Before the breath test takes place, the administering officer must read the driver a standard form which states that:

•  The driver must submit to the breath test under penalty of law, and

•  The driver has the right to observe the results of the test on the digital screen (not just on the print out).

Every driver tested in Virginia should exercise the right to observe the results for himself.

When a driver is ready to take the ETD breath test, he will blow at least two times. The machine will take two samples and print out the lesser of the two readings. If the machine detects any errors, an error screen will appear, and the machine will print out an error message that may be used as evidence of refusal to submit to a breath test.

The INTOX EC/IR II works the same way as the PBT with two notable exceptions. First, the PBT uses only an electrochemical (EC) process to determine BAC while the INTOX EC/IR II uses EC and infrared (IR) analysis to determine BAC.

IR analysis, called infrared spectroscopy, works by shooting infrared light through a sample of breath and measuring how much of the light makes it through the sample. The light is of a specific wavelength that is absorbed by alcohol so the less light that makes it through the breath sample, the greater the concentration of alcohol in the sample.

The second difference between ETDs and PBTs is that the ETDs have the ability to detect certain errors. The INTOX EC/IR II can detect some levels of radio frequency interference (RFI). It can also detect alcohol left over inside the machine or in the air around the machine. In addition, it can run a limited self-diagnosis and will shut itself off if it detects certain errors.

Despite all of these bells and whistles, the INTOX EC/IR II is still a machine and subject to error and technical glitches.

All breathalyzers work on the principle that the alcohol in a person’s blood evaporates into the lungs at a predictable rate. These machines make assumptions about the BAC based on the percentage of alcohol in a person’s breath. However, as with all assumptions, there are potential flaws.

Anyone who has watched a pot of water boil knows that as the water gets warmer, more of it evaporates (steams). Alcohol is the same. As the human body warms up, the percentage of alcohol vapors in the lungs rises. Breathalyzers do not take a person’s temperature; they simply assume that a person’s body temperature is 98.6°Fahrenheit. However, if the driver’s body temperature is over 98.6°when the test is conducted, then the machine will return an erroneously high BAC reading. Consequently, if a person has a fever, is dressed too warm, or is even left in a hot room too long, the breath test may be artificially high.

Another flaw with breathalyzers (including the INTOX EC/IR II) is that they assume that all of the alcohol detected came from the driver’s lungs. Alcohol fumes from a person’s stomach, mouth, or throat are much more potent than the fumes from the lungs. A person that has recently consumed alcohol, burped, or vomited will produce a BAC breath result that is much higher than reality.

Because of this problem, police officers in Virginia must “observe” the driver for 20 minutes before administering a breath test at the police station. During this time, they are supposed to look for signs that the driver has burped, vomited, or put anything into his mouth.

If you drank, vomited or burped 20 minutes before taking a breath test, make sure you inform your attorney immediately.

Another weakness of breathalyzers is one of all machines: they get old and break down. That is why the legislature mandates that any ETD used in Virginia needs to be calibrated by the Department of Forensic Science (DFS) every six months. In order to introduce an ETD result as evidence in a trial, the court may require breath technicians to produce evidence of regular maintenance and calibration of the ETD.

Breathalyzer results may also be affected by the amount of breath sample given. When someone has been drinking, there are more alcohol fumes in the deepest portions of their lungs than there are at the top.

The police want you to take a great big breath and blow really hard, so that you exhale as much of that alcohol-rich air in the bottom of your lungs as possible. Your attorney can obtain and examine the exact blow duration and breath volume for your test.

Blood Testing

If a driver is arrested for DUI and is suspected of being under the influence of drugs, or is physically incapable of giving a breath sample (e.g. he has passed out), the police may choose to take a blood sample in addition to or as a substitute for a breath test.

A driver who has been arrested for DUI or DWI is required by law to submit to a blood test just as he is for a breath test. However, a driver must submit only if he has been arrested. If a driver is in the hospital and the police have not arrested him for DUI, they must ask for permission to take his blood sample. If your blood was sampled without your permission, talk to your attorney immediately to determine whether your rights were infringed upon.

Whether a driver is under arrest is not always clear, especially when a driver is in the hospital and is not placed in handcuffs or taken away.

Since 1995, the police do not have to offer the blood test as a substitute for the breath test. A driver can request a blood test, but the police do not have to give one. They often do not want to wait for the results of the blood test, which take longer. Requesting a blood test is not a complete defense to being charged with refusal to submit to a breath test. If a driver balks at submitting to a blood test the police must notify the driver that refusing to comply with the blood sample means they will be charged with refusal to submit.

Blood tests, like the breath tests, are regulated by Virginia law. Failure to comply with the procedures and methods specified by law may cause the results to be excluded from a DUI trial.

The person drawing the blood must be an approved medical worker. When blood is draw at the police station, the blood must be kept in two separate vials supplied by the Department of Forensic Science (DFS), and must be sealed and accompanied by two completed certificates of withdrawal. The vials must then be placed in a DFS-approved container and delivered to the officer.

The vials then go to DFS and are tested for alcoholic content via a method called “gas chromatography.” Gas chromatography detects the amount of ethanol (the alcohol found in liquor) in the blood by vaporizing the alcohol in a specific quantity of blood and then quantifying the vaporized gas that escapes.

After the test is complete, a certificate of analysis is produced. The certificate must contain certain mandatory information about the driver, and it must be returned with the nurse’s certificate of withdrawal to the court. Failure to return the certificate of analysis attached to the nurse’s certificate of withdrawal may result in dismissal of the case.

The second vial is sent to DFS and is held for 90 days. The defense attorney can then have the vial sent to an independent laboratory for testing. If DFS loses the independent sample, the BAC results should be excluded from evidence. A good DUI attorney should always request independent testing, especially since the blood alcohol content of a sample tends to diminish after the blood is taken, and the second test will often be lower.

Not all blood tests are performed by police personnel. Sometimes hospitals run the blood test, especially when the driver is hospitalized due to an accident. Because the law allows the results of hospital blood analysis to be used in trial, and because each hospital has a different process for drawing and testing blood, defense attorney dealing with blood samples need to be aware of the varying methods used to test BAC. This fact is another reason to hire an attorney that specializes in DUI defense.

Typically, hospitals use the enzymatic method for determining BAC. However, one flaw of this method is that it tends to produce erroneously high readings if certain chemicals caused by tissue trauma are present in the blood. For instance, drivers who sustain bruises in an accident may produce erroneously high BAC readings.

Blood-sample analysis is highly technical and requires a DUI attorney who is not only experienced but is also familiar with the forensic science behind these complicated DUI testing methods.